Developing device for wet process electrophotography

ABSTRACT

A developing device for a wet process electrophotography wherein within a developing solution chamber are disposed a wetting roller whose lower portion is immersed in the developing solution and a developing roller in parallel with the wetting roller in such a manner that a developing solution reservoir may be produced between the two rollers upon rotation thereof, the wetting roller being applied with a potential having the polarity same as that of the tonner in the developing solution while the developing roller, a potential having the polarity opposite to that of the tonner; and a sensitized member is fed with its surface facing against the two rollers through the developing chamber. The device may be made in compact in size even though it is provided with means for prewetting the sensitized member.

United States Patent DEVELOPING DEVICE FOR WET PROCESS ELECTROPHOTOGRAPHY 4 Claims, 5 Drawing Figs.

US. Cl 118/637, 117/175, 117/37 LE Int. Cl D05b 5/00 Field of Search 95/89;

1l7/l7.5, 37 LE; 118/637 Primary Examiner-Henry S. Jaudon Attorney- Burgess, Ryan and Hicks ABSTRACT: A developing device for a wet process electrophotography wherein within a developing solution chamber are disposed a wetting roller whose lower portion is immersed in the developing solution and a developing roller in parallel with the wetting roller in such a manner that a developing solution reservoir may be produced between the two rollers upon rotation thereof, the wetting roller being applied with a potential having the polarity same as that of the tonner in the developing solution while the developing roller, a potential having the polarity opposite to that of the tonner; and a sensitized member is fed with its surface facing against the two rollers through the developing chamber. The device may be made in compact in size even though it is provided with means for prewetting the sensitized member.

DEVELOPING DEVICE FOR WET PROCESS ELECTROPI-IOTOGRAPHY BACKGROUND OF THE INVENTION developing an electrostatic latent image formed upon a photoconductive material layer of a sensitized member by charging and exposure. It is well known in the art that a better quality image may be reproduced in the wet process electrophotography when the sensitized member is previously wetted by a solution similar to the carrier prior to the development by the developing solution. For this purpose, an independent prewetting device must be provided in a developing device so that the electrophotographic copying machine tends to become bulky in size, heavy in weight and complicated in operation.

SUMMARY OF THE INVENTION The present invention therefore has its first object to provide a developing device for wet process electrophotography having a prewetting function, thereby eliminating the need of provision of an independent prewetting device in the developing device, whereby the electrophotographic copying machine can be made compact in size, inexpensive to manufacture and simple and reliable in operation.

According to the present invention, a wetting roller and a developing are juxtaposed. The wetting roller is applied with a potential having the same polarity as that of the toner while the developing roller, a potential having the polarity opposite to that of the toner. At least one of the two rollers is partially immersed in the developing solution so that upon rotation of the rollers a developing solution reservoir is formed therebetween or the developing solution is attached to the peripheral surfaces of the two rollers to a thickness depending upon the viscosity of the developing solution. A sensitized member is fed with its surface (photoconductive layer) facing toward the two rollers. Since the wetting roller is applied with the potential having the same polarity as that of the toner, the developing solution in the proximity of the peripheral surface of this wetting roller has a relatively low toner concentration. On the other hand, the developing roller is applied with the potential having the polarity opposite to that of the tone so that the developing solution in the proximity of the peripheral surface thereof has a relatively higher toner concentration. The sensitized member is first applied with the developing solution having a relatively lower toner concentration by the wetting roller and thereafter is developed by the developing solution having a relatively high toner concentration.

According to the present invention, the sensitized member may be prewetted and developed only by the developing device so that the image having a better quality may be reproduced. Since the independent wetting device can be eliminated, the electrophotographic copying machine can be made compact in size, inexpensive to manufacture and simple in operation.

According to one embodiment of the present invention, a guide roller is provided so that the sensitized member may not be spaced away from the wetting and developing roller in ex cess of a predetermined distance or gap. According to another embodiment of the present invention, instead of said guide roller, means provided with a plurality of air blowing means arranged in one row may be used so that the contamination of the back surface of the sensitized member by the developing solution can be advantageously prevented and the waste of the developing solution can be also prevented.

The above and other objects, features and advantages of the present invention will become more apparent from the following description of some illustrative embodiments thereof taken in conjunction with the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a sectional view of one embodiment of a developing device in accordance with the present invention;

FIG. 2 is a fragmentary plan view illustrating the constructions and arrangement of a wetting and developing rollers thereof;

FIGS. 3 and 4 are sectional views illustrating a second and third embodiments of the present invention; and

FIG. 5 is a perspective view illustrating one example of an air-blowing pipe used in the developing device of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring first to FIG. 1, a wetting roller 3 which is rotated in the direction indicated by an arrow a by a suitable driving means (not shown) has its outer peripheral surface partially immersed in a developing solution 2 contained in a developing chamber or reservoir 1, and a developing roller 4 is pressed against the wetting roller 3 and is rotated in the direction indicated by an arrow b. The trunnions 3a and 4a of the wetting roller 3 and the developing roller 4 are loosely journaled by bearing members 112 and 1c respectively (See FIG. 2) which in turn are securely fixed to each of the sidewalls la of the developing chamber 1. The wetting and developing rollers 3 and 4 are provided with flanges 3b and 4b formed at both ends thereof respectively. Inwardly of the flange 3b of the wetting roller 3 is formed an annular groove 30 (See FIG. 2) into which is fitted the flange 4b of the developing roller 4.

Both of the wetting and developing rollers 3 and 4 are.electrically connected to a power source 5 in such a manner that the potential having the same polarity of that of the toner in the developing solution 2 may be applied to the wetting roller 3 while the potential having the polarity opposite to the toner may be applied to the developing roller 4. A variable resistor 6 is circuited on the side of the roller 4 so that the potential applied thereto may be suitably adjusted. Upon rotation of the wetting roller 3 in the direction of the arrow a, the developing solution 2 is conveyed upon the peripheral surface of the wetting roller 3 and is stored in a somewhat wedge-shaped recess or space defined by both of the rollers 3 and 4. Since the flanges 3b and 4b are so arranged as to overlap one upon another as best shown in FIG. 2, the stored developing solution 2 may be prevented from dropping from the both sides of the wetting and developing rollers 3 and 4. Thus, the developing solution 2 is generally flown down upon the peripheral surface of the developing roller 4. It is understood that instead of the flanges 3b and 4b described hereinabove any suitable developing solution leakage preventing means may be used and that if needs demand such means may be eliminated.

As described above, the wetting roller 3 is applied with the potential having the same polarity as that of the toner so that the toner tends to be repelled from the peripheral surface of the wetting roller, whereby the toner concentration in the proximity of the peripheral surface of the wetting roller is relatively low. The developing solution 2a being conveyed upon the peripheral surface of the wetting roller 3 has also a relatively low toner concentration because of the same reason described hereinabove. On the other hand, the potential having the polarity opposite to that of the toner is applied to the developing roller so that the toner in the developing solution 2 in the proximity of the developing roller 4 is attracted toward it. Consequently, the toner concentration of the developing solution 2b in the proximity of the developing roller 4 is equal to or in excess of that of the developing solution 2. This means that the developing solution 2b has regained its developing power sufficiently.

Referring still FIG. 1, a sensitized member 7 is fed in the direction indicated by an arrow c by a suitable feeding means (not shown) in such a manner that the electrostatic latent image forming surface is faced downwardly toward the wetting roller 3. The image-forming surface is first applied with a low toner concentration developing solution 2 around the wetting roller 3 and thereafter is developed by a relatively high toner concentration developing solution 2b around the developing roller 4. A guide roller 8 is provided for preventing the sensitized member 7 from moving away from the wetting roller 3. It is understood that instead of this guide roller 8, any suitable guide means may be used.

In one embodiment of the present invention illustrated in FIG. 3, instead of the developing roller 4 in the first embodiment a roller 31 which contacts with the wetting roller may be partially immersed in the developing solution 2. In one form of the present invention, both of the wetting and developing rollers 3 and 31 may be spaced apart from each other by a small distance and are driven independently.

In the embodiment illustrated in FIGS. 4 and 5, instead of the guide roller 8 of the first embodiment, an air-blowing pipe 41 having a plurality of small holes 4111 may be disposed in such a manner that the pipe 41 is coupled to a blower 42, thereby making the sensitized member 7 in contact with the developing solution under the pressure of the air blown from the pipe 41 In one modification of the present invention, instead of the pipe 41, a plurality of nozzles may be provided.

When such air-blowing devices as described above are used, the air blows off the developing solution upon the back surface of the sensitized member 7 to that only the electrostatic latent image forming surface of the sensitized member 7 is applied with a suitable quantity of developing solution 2, whereby the waste of the developing solution 2 may be advantageously prevented and the stain or the like may be also prevented from being formed upon the back surface of the sensitized member 7. Furthermore, it is only necessary to dry only one surface or the electrostatic latent image forming surface of the sensitized member 7 so that the fixing of the toner can be advantageously and immediately effected by use of a simple drying device.

In the second and third embodiments shown in FIGS. 3, 4

and 5 same parts are designated by same reference numerals as in the case ofthe first embodiment described with reference to FIGS. 1 and 2. No further description of the second and third embodiments as to their constructions, arrangement and mode of operation will be made hereinafter because they are readily understood from the description of the first embodiment.

Iclaim:

1. A developing device for wet comprising a sensitized member wetting roller applied with a potential having the same polarity as that of the toner in the developing solution,

a developing roller juxtaposed with said wetting roller and applied with a potential having the polarity opposite to that of the toner,

means for driving said wetting and developing rollers, and

guide means for a sensitized member,

peripheral surface portion of at least one of said wetting and developing rollers being immersed in the developing solution,

said sensitized member being fed with its electrostatic latent image forming and developing surface faced against said wetting roller so as to contact with the developing solution around said wetting roller.

2. A developing device for wet process electrophotography as defined in claim 1 wherein said guide means comprises a roller.

3. A developing device for wet process electrophotography as defined in claim 1 wherein said guide means comprises an air-blowing pipe having a plurality of small diameter holes formed therethrough in the direction of the axis of said pipe.

4. A developing device for wet process electrophotography as defined in claim 1 wherein said guide means comprises an air-blowing device having a plurality of nozzles.

process electrophotography 

1. A developing device for wet process electrophotography comprising a sensitized member wetting roller applied with a potential having the same polarity as that of the toner in the developing solution, a developing roller juxtaposed with said wetting roller and applied with a potential having the polarity opposite to that of the toner, means for driving said wetting and developing rollers, and guide means for a sensitized member, peripheral surface portion of at least one of said wetting and developing rollers being immersed in the developing solution, said sensitized member being fed with its electrostatic latent image forming and developing surface faced against said wetting roller so as to contact with the developing solution around said wetting roller.
 2. A developing device for wet process electrophotography as defined in claim 1 wherein said guide means comprises a roller.
 3. A developing device for wet process electrophotography as defined in claim 1 wherein said guide means comprises an air-blowing pipe having a plurality of small diameter holes formed therethrough in the direction of the axis of said pipe.
 4. A developing device for wet process electrophotography as defined in claim 1 wherein said guide means comprises an air-blowing device having a plurality of nozzles. 